JP2680746B2 - Pulse noise removal circuit - Google Patents
Pulse noise removal circuitInfo
- Publication number
- JP2680746B2 JP2680746B2 JP3141961A JP14196191A JP2680746B2 JP 2680746 B2 JP2680746 B2 JP 2680746B2 JP 3141961 A JP3141961 A JP 3141961A JP 14196191 A JP14196191 A JP 14196191A JP 2680746 B2 JP2680746 B2 JP 2680746B2
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- Prior art keywords
- circuit
- noise
- pulse noise
- signal
- pulse
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、ＦＭラジオ受信機で受
信された受信信号中に含まれるパルスノイズを除去する
ためのパルスノイズ除去回路に関するもので、特に弱電
界受信時における情報量の減少を防止せんとするもので
ある。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse noise removing circuit for removing pulse noise contained in a reception signal received by an FM radio receiver, and more particularly to reducing the amount of information when receiving a weak electric field. It is intended to prevent
【０００２】[0002]
【従来の技術】耳障りなパルスノイズを除去する為、受
信信号中に含まれるパルスノイズを検出し、少なくとも
前記パルスノイズの発生期間中、信号路に配置されるゲ
ート回路を制御し、ノイズの発生を防止するパルスノイ
ズ除去回路が知られている。しかして、このようなパル
スノイズ除去回路においては、パルスノイズに応じて動
作するゲート信号発生回路を備えており、該ゲート信号
発生回路から発生するゲート信号のパルス幅に対応する
期間中、パルスノイズの除去が行われる。2. Description of the Related Art In order to remove annoying pulse noise, pulse noise contained in a received signal is detected, and a gate circuit arranged in a signal path is controlled at least during the period of generation of the pulse noise to generate noise. There is known a pulse noise removing circuit for preventing the noise. Therefore, such a pulse noise removing circuit is provided with a gate signal generating circuit that operates according to the pulse noise, and the pulse noise is generated during the period corresponding to the pulse width of the gate signal generated from the gate signal generating circuit. Are removed.
【０００３】[0003]
【発明が解決しようとする課題】従来のパルスノイズ除
去回路は、ゲート信号のパルス幅がパルスノイズを効果
的に除去し得る所定値に、例えば４０μＳに固定されて
いた。このパルスノイズ除去回路は、自動車のイグニッ
ションノイズ等のパルスノイズを効果的に除去すること
ができる。In the conventional pulse noise removing circuit, the pulse width of the gate signal is fixed to a predetermined value capable of effectively removing the pulse noise, for example, 40 μS. The pulse noise removing circuit can effectively remove pulse noise such as automobile ignition noise.
【０００４】しかしながら、弱電界受信時においては、
前記パルスノイズ除去回路が過変調ノイズ等によって誤
動作するという問題が生じる。即ち、弱電界受信時に
は、弱電界ノイズのレベルが大になるが、この弱電界ノ
イズは、ノイズＡＧＣによりそのレベルが抑圧され、パ
ルスノイズ検出回路で検出されない。ところが、弱電界
時に過変調ノイズが混入すると、弱電界ノイズに過変調
ノイズが重畳されてパルス的となり、しかもこのノイズ
がパルスノイズよりも大なる頻度で発生する。この疑似
パルスノイズは、パルスノイズ検出回路で検出され、ゲ
ートを頻繁に開閉する。その為、ゲートの開期間中必要
な情報が失われるという問題が生じる。However, when receiving a weak electric field,
There is a problem that the pulse noise removing circuit malfunctions due to overmodulation noise or the like. That is, when the weak electric field is received, the level of the weak electric field noise becomes large, but the level of the weak electric field noise is suppressed by the noise AGC and is not detected by the pulse noise detection circuit. However, if the overmodulation noise is mixed in during the weak electric field, the overmodulation noise is superimposed on the weak electric field noise and becomes pulse-like, and the noise is generated at a frequency higher than the pulse noise. This pseudo pulse noise is detected by the pulse noise detection circuit, and the gate is frequently opened and closed. Therefore, there arises a problem that necessary information is lost during the opening period of the gate.
【０００５】最近は、パルスノイズによる受信妨害より
も、上述の疑似パルスノイズによる情報消失のほうがよ
り問題となってきた。Recently, the loss of information due to the pseudo pulse noise described above has become a more serious problem than the reception interference due to pulse noise.
【０００６】[0006]
【課題を解決するための手段】本発明は、上述の点に鑑
み成されたもので、疑似パルスノイズに対しても効果の
あるパルスノイズ除去回路を提供せんとするもので、パ
ルスノイズ検出回路と、ゲート信号発生回路と、ゲ−ト
回路と、受信信号の電界強度又は受信信号中に含まれる
連続ノイズの量に応じてゲート信号発生回路を制御する
制御回路とを備える点を特徴とする。SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is intended to provide a pulse noise removing circuit which is also effective against pseudo pulse noise. A gate signal generating circuit, a gate circuit, and a control circuit for controlling the gate signal generating circuit according to the electric field strength of the received signal or the amount of continuous noise contained in the received signal. .
【０００７】[0007]
【作用】本発明によれば、中強電界時には、ゲート信号
発生回路の出力パルス幅を大（約４０μＳ）とすること
が出来るので、イグニッションノイズ等の比較的発生周
期の長いパルスノイズを有効に除去することができる。
又、弱電界時には、ゲート信号発生回路の出力パルス幅
を小（約２０μＳ）とすることが出来るので、頻度の高
い過変調ノイズ等に起因する情報消失を防止できる。According to the present invention, since the output pulse width of the gate signal generating circuit can be made large (about 40 μS) at the time of a medium and strong electric field, pulse noise having a relatively long generation period such as ignition noise can be effectively used. Can be removed.
Further, when the electric field is weak, the output pulse width of the gate signal generating circuit can be made small (about 20 μS), so that information loss due to frequent overmodulation noise and the like can be prevented.
【０００８】[0008]
【実施例】図１は、本発明の一実施例を示す回路図で、
(１)は受信アンテナ、(２)はアンテナ(１)に受信された
ＲＦ信号を増幅するＲＦ増幅回路、(３)はＲＦ増幅回路
(２)の出力信号と局部発振回路(４)の出力信号とを混合
する混合回路、(５)は混合回路(３)の出力ＩＦ信号を増
幅するＩＦ増幅回路、(６)はＩＦ増幅回路の出力ＩＦ信
号をＦＭ検波するＦＭ検波回路、(７)はＦＭ検波回路
(６)の出力端に接続されたバッファ回路、(８)はバッフ
ァ回路(７)の出力信号中に含まれるパルスノイズを除去
するゲート回路、(９)はＦＭ検波回路(６)の出力信号中
に含まれる高周波ノイズ成分を通過させるハイパスフィ
ルター、(10)はパルスノイズ検出回路、(11)はハイパス
フィルタ(９)の出力信号中に含まれる連続ノイズに応じ
てＡＧＣを行うノイズＡＧＣ回路、(12)はパルスノイズ
検出回路(10)の出力信号に応じて動作する単安定マルチ
バイブレータ、(13)は受信信号の電界強度を示す信号を
発生する制御回路、(14)は制御回路(13)の出力信号に応
じて単安定マルチバイブレータ(11)の時定数を切換える
時定数切換回路である。尚、単安定マルチバイブレータ
(12)と時定数切換回路(14)とは、ゲート信号発生回路を
構成している。FIG. 1 is a circuit diagram showing an embodiment of the present invention.
(1) is a receiving antenna, (2) is an RF amplifier circuit for amplifying the RF signal received by the antenna (1), (3) is an RF amplifier circuit
A mixing circuit that mixes the output signal of (2) and the output signal of the local oscillator circuit (4), (5) an IF amplification circuit that amplifies the output IF signal of the mixing circuit (3), and (6) an IF amplification circuit. FM detection circuit for FM detection of the output IF signal of (7) is an FM detection circuit
A buffer circuit connected to the output terminal of (6), (8) a gate circuit for removing pulse noise contained in the output signal of the buffer circuit (7), and (9) an output signal of the FM detection circuit (6). A high-pass filter that passes the high-frequency noise component contained therein, (10) is a pulse noise detection circuit, (11) is a noise AGC circuit that performs AGC according to the continuous noise contained in the output signal of the high-pass filter (9), (12) is a monostable multivibrator that operates according to the output signal of the pulse noise detection circuit (10), (13) is a control circuit that generates a signal indicating the electric field strength of the received signal, and (14) is a control circuit (13 ) Is a time constant switching circuit for switching the time constant of the monostable multivibrator (11) in accordance with the output signal of (1). In addition, monostable multivibrator
The (12) and the time constant switching circuit (14) form a gate signal generating circuit.
【０００９】次に動作を説明する。アンテナ(１)に受信
された信号は、ＲＦ増幅回路(２)で増幅されたのち混合
回路(３)において局部発振回路(４)の出力信号と混合さ
れ、ＩＦ信号に変換される。前記ＩＦ信号は、ＩＦ増幅
回路(５)で増幅され、ＦＭ検波回路(６)でＦＭ検波され
る。その後、ＦＭ検波回路(６)の出力信号は、バッファ
回路(７)及びゲート回路(８)を介して出力端子に導出さ
れる。Next, the operation will be described. The signal received by the antenna (1) is amplified by the RF amplifier circuit (2) and then mixed with the output signal of the local oscillation circuit (4) in the mixing circuit (3) to be converted into an IF signal. The IF signal is amplified by the IF amplification circuit (5) and FM-detected by the FM detection circuit (6). After that, the output signal of the FM detection circuit (6) is led to the output terminal via the buffer circuit (7) and the gate circuit (8).
【００１０】ＦＭ検波回路(６)の出力信号中の高周波ノ
イズ成分は、ハイパスフィルター(９)を通過し、パルス
ノイズ検出回路(10)に印加され、そこでパルスノイズの
検出が行われる。パルスノイズ検出回路(10)に対して
は、ノイズＡＧＣ回路(11)によって連続ノイズレベルに
応じたＡＧＣがかけられているので、パルスノイズ検出
回路(10)は所定レベル以上のパルスノイズのみを検出す
ることができる。検出されたパルスノイズは、単安定マ
ルチバイブレータ(12)にトリガとして印加される。その
為、単安定マルチバイブレータ(12)の出力には、検出さ
れたパルスノイズのタイミングを持ち、所定のパルス幅
を持ったゲート信号が発生する。The high frequency noise component in the output signal of the FM detection circuit (6) passes through the high pass filter (9) and is applied to the pulse noise detection circuit (10) where pulse noise is detected. Since the noise AGC circuit (11) applies AGC according to the continuous noise level to the pulse noise detection circuit (10), the pulse noise detection circuit (10) detects only pulse noise above a predetermined level. can do. The detected pulse noise is applied to the monostable multivibrator (12) as a trigger. Therefore, at the output of the monostable multivibrator (12), a gate signal having the timing of the detected pulse noise and a predetermined pulse width is generated.
【００１１】ところで、単安定マルチバイブレータ(12)
の時定数は、時定数切換回路(14)の出力に応じて切換わ
る。今、受信信号の電界強度が中または強であるとすれ
ば、電界強度を検出する制御回路(13)の出力信号は、第
１の値（例えばＬ）となり、時定数切換回路(14)の出力
信号も第１の値となり、単安定マルチバイブレータ(12)
の時定数は比較的長い第１の値（例えば４０μＳ）とな
る。その為、ゲート信号のパルス幅（４０μＳ）が、パ
ルスノイズを効果的に除去し得る値となり、図１のパル
スノイズ除去回路は、除去機能を十分に発揮する。By the way, the monostable multivibrator (12)
The time constant of is switched according to the output of the time constant switching circuit (14). Now, assuming that the electric field strength of the received signal is medium or strong, the output signal of the control circuit (13) for detecting the electric field strength becomes the first value (for example, L), and the output of the time constant switching circuit (14). The output signal also becomes the first value, and the monostable multivibrator (12)
The time constant of is a relatively long first value (for example, 40 μS). Therefore, the pulse width (40 μS) of the gate signal has a value that can effectively remove the pulse noise, and the pulse noise removal circuit of FIG. 1 sufficiently exhibits the removal function.
【００１２】一方、受信信号の電界強度が弱くなると、
制御回路(13)の出力信号が第２の値（たとえばＨ）とな
り、時定数切換回路(14)の値も第２の値となり、単安定
マルチバイブレータ(12)の時定数は比較的短い第２の値
（例えば２０μＳ）となる。その為、弱電界受信時に、
過変調ノイズ等が発生し、単安定マルチバイブレータ(1
2)が動作し、ゲート回路(８)が動作したとしても、信号
及びノイズの遮断期間が短くなり、情報の消失量が少な
くなる。一般に、弱電界受信時には、ノイズ量が多くな
るので、パルスノイズの除去よりも情報の確保を優先し
たほうが、聴取者に対し良好な受信を提供し得る。On the other hand, when the electric field strength of the received signal becomes weak,
The output signal of the control circuit (13) becomes the second value (for example, H), the value of the time constant switching circuit (14) becomes the second value, and the time constant of the monostable multivibrator (12) is relatively short. The value is 2 (for example, 20 μS). Therefore, when receiving a weak electric field,
Over-modulation noise etc. occurs and monostable multivibrator (1
Even if 2) is activated and the gate circuit (8) is activated, the signal and noise cutoff period is shortened and the amount of information lost is reduced. In general, when receiving a weak electric field, the amount of noise is large, so prioritizing the securing of information over removal of pulse noise can provide better reception to the listener.
【００１３】上述の説明においては、受信信号が弱電界
であることを、受信信号の電界強度を検出する制御回路
(13)を用いて検出している。しかしながら、弱電界の検
出は、他の方法、例えば、ノイズＡＧＣ回路を用いるこ
とによっても検出することができる。即ち、図１に示す
如く、弱電界時に大となる連続ノイズをノイズＡＧＣ回
路(11)から取り出し、制御回路(13')でそのレベルを検
出して制御信号を発生すれば、弱電界時に時定数切換回
路(14)を制御することができ、制御回路(13)を用いた場
合と全く同じ結果を得ることができる。In the above description, the control circuit for detecting the electric field strength of the received signal indicates that the received signal is a weak electric field.
It is detected using (13). However, the weak electric field can be detected by another method, for example, by using a noise AGC circuit. That is, as shown in FIG. 1, continuous noise that becomes large in a weak electric field is extracted from the noise AGC circuit (11), and its level is detected by the control circuit (13 ') to generate a control signal. It is possible to control the constant switching circuit (14) and obtain exactly the same result as when the control circuit (13) is used.
【００１４】図２は、図１の単安定マルチバイブレータ
(12)及び時定数切換回路(14)の具体回路例を示す回路図
である。図２において、入力端子(15)には、図１のパル
スノイズ検出回路(10)の出力信号が印加される。前記入
力端子(15)に信号が印加されると、トランジスタ(16)が
オンし、コンデンサ(17)の充電が行われる。コンデンサ
(17)が放電している初期状態においては、トランジスタ
(18)がオフ、トランジスタ(19)がオンとなっている。そ
の為、トランジスタ(20)がオン、トランジスタ(21)がオ
フとなり、出力端子(22)にＬレベルの出力信号が発生し
ている。コンデンサ(17)の充電が進みトランジスタ(18)
のベース電圧がトランジスタ(19)のベース電圧を越える
と、トランジスタ(18)がオン、トランジスタ(19)がオフ
となり、トランジスタ(20)がオフ、トランジスタ(21)が
オンとなって、出力端子(22)にＨレベルの出力信号が発
生する。その後、コンデンサ(17)の電荷は、抵抗(23)を
介して放電され、トランジスタ(18)のベ−ス電圧がトラ
ンジスタ(19)のベース電圧よりも低下すると、再びトラ
ンジスタ(18)がオフ、トランジスタ(19)がオンとなり、
トランジスタ(20)がオン、トランジスタ(21)がオフとな
って、出力信号がＬレベルとなる。コンデンサ(17)と抵
抗(23)との放電時定数は、約４０μＳに設定されている
ので、出力端子(22)に得られる出力信号のパルス幅も約
４０μＳとなる。FIG. 2 is a monostable multivibrator of FIG.
It is a circuit diagram showing a concrete circuit example of (12) and a time constant switching circuit (14). In FIG. 2, the output signal of the pulse noise detection circuit (10) of FIG. 1 is applied to the input terminal (15). When a signal is applied to the input terminal (15), the transistor (16) is turned on and the capacitor (17) is charged. Capacitor
In the initial state when (17) is discharging, the transistor
(18) is off and transistor (19) is on. Therefore, the transistor (20) is turned on, the transistor (21) is turned off, and an L level output signal is generated at the output terminal (22). Charge of the capacitor (17) progresses and transistor (18)
When the base voltage of exceeds the base voltage of the transistor (19), the transistor (18) turns on, the transistor (19) turns off, the transistor (20) turns off, the transistor (21) turns on, and the output terminal ( An output signal of H level is generated at 22). After that, the electric charge of the capacitor (17) is discharged through the resistor (23), and when the base voltage of the transistor (18) becomes lower than the base voltage of the transistor (19), the transistor (18) is turned off again, The transistor (19) is turned on,
The transistor (20) is turned on, the transistor (21) is turned off, and the output signal becomes L level. Since the discharge time constant of the capacitor (17) and the resistor (23) is set to about 40 μS, the pulse width of the output signal obtained at the output terminal (22) is also about 40 μS.
【００１５】中強電界受信時には、図１の制御回路(13)
の出力信号がＬレベルとなっているので、トランジスタ
(24)がオフとなり、コンデンサ(17)の放電時定数は上述
の如くコンデンサ(17)の容量と抵抗(23)の抵抗値とによ
って定まる。又、弱電界受信時には、制御回路(13)の出
力信号がＨレベルとなるので、トランジスタ(24)がオン
となり、コンデンサ(17)の放電時定数は、コンデンサ(1
7)の容量と抵抗(23)及び(25)の並列抵抗値とによって定
まる。抵抗(25)の抵抗値を適切に定めれば、弱電界受信
時におけるコンデンサ(17)の放電時定数を２０μＳにす
ることができ、出力端子(22)に得られる出力信号のパル
ス幅を約２０μＳにすることができる。When receiving a medium strong electric field, the control circuit (13) shown in FIG.
Since the output signal of is at L level,
(24) is turned off, and the discharge time constant of the capacitor (17) is determined by the capacitance of the capacitor (17) and the resistance value of the resistor (23) as described above. Further, when the weak electric field is received, the output signal of the control circuit (13) becomes H level, the transistor (24) is turned on, and the discharge time constant of the capacitor (17) is
It is determined by the capacitance of 7) and the parallel resistance value of the resistors (23) and (25). If the resistance value of the resistor (25) is set appropriately, the discharge time constant of the capacitor (17) at the time of receiving a weak electric field can be set to 20 μS, and the pulse width of the output signal obtained at the output terminal (22) is about It can be 20 μS.
【００１６】[0016]
【発明の効果】以上述べた如く、本発明によれば、パル
スノイズを検出したとき、受信信号の電界強度に応じて
ゲート駆動用のパルスの幅を変更することができるの
で、中強電界時にはパルス幅を広くしてパルスノイズを
確実に除去することができ、弱電界時にはパルス幅を狭
くして情報の不要な消失を防止できる。As described above, according to the present invention, when the pulse noise is detected, the width of the gate driving pulse can be changed according to the electric field strength of the received signal. The pulse width can be widened to reliably remove pulse noise, and the pulse width can be narrowed in a weak electric field to prevent unnecessary loss of information.
【図１】本発明の一実施例を示す回路図FIG. 1 is a circuit diagram showing one embodiment of the present invention.
【図２】図１の単安定マルチバイブレータ(12)及び時定
数切換回路(14)の具体回路例を示す回路図FIG. 2 is a circuit diagram showing a specific circuit example of a monostable multivibrator (12) and a time constant switching circuit (14) of FIG.
(８) ゲート回路 (10) パルスノイズ検出回路 (11) ノイズＡＧＣ回路 (12) 単安定マルチバイブレータ (13) 制御回路 (14) 時定数切換回路 (8) Gate circuit (10) Pulse noise detection circuit (11) Noise AGC circuit (12) Monostable multivibrator (13) Control circuit (14) Time constant switching circuit
Claims (2)
めのパルスノイズ除去回路であって、受信信号中に含ま
れるパルスノイズを検出する検出回路と、該検出回路の
出力信号に応じてゲ−ト信号を発生するゲート信号発生
回路と、前記ゲート信号に応じてパルスノイズを除去す
るゲ−ト回路と、受信信号の電界強度または受信信号中
に含まれる連続ノイズに応じて前記ゲート信号発生回路
を制御する制御回路とからなるパルスノイズ除去回路。1. A pulse noise removal circuit for removing pulse noise in a received signal, the detection circuit detecting pulse noise included in the received signal, and a gate circuit according to an output signal of the detection circuit. A gate signal generating circuit for generating a pulse signal, a gate circuit for removing pulse noise according to the gate signal, and a gate signal generating circuit according to the electric field strength of the received signal or continuous noise contained in the received signal Pulse noise removal circuit consisting of a control circuit for controlling the.
チバイブレータからなり、前記制御回路は前記単安定マ
ルチバイブレータの時定数を制御することを特徴とする
請求項１記載のパルスノイズ除去回路。2. The pulse noise elimination circuit according to claim 1, wherein the gate signal generation circuit comprises a monostable multivibrator, and the control circuit controls a time constant of the monostable multivibrator.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3141961A JP2680746B2 (en) | 1991-06-13 | 1991-06-13 | Pulse noise removal circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3141961A JP2680746B2 (en) | 1991-06-13 | 1991-06-13 | Pulse noise removal circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04365229A JPH04365229A (en) | 1992-12-17 |
| JP2680746B2 true JP2680746B2 (en) | 1997-11-19 |
Family
ID=15304154
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3141961A Expired - Lifetime JP2680746B2 (en) | 1991-06-13 | 1991-06-13 | Pulse noise removal circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2680746B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3573050B2 (en) * | 2000-02-23 | 2004-10-06 | 三菱電機株式会社 | Noise removal device |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3009542U (en) * | 1994-09-28 | 1995-04-04 | 瀧定株式会社 | Hanging hook |
-
1991
- 1991-06-13 JP JP3141961A patent/JP2680746B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04365229A (en) | 1992-12-17 |
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